ramblinboy Report post Posted March 20, 2012 Saw Pilot/Flying J prices from the freeway. Sure their prices look low but that gas price is 85 octane. My Ford F53 pings with low octane fuel. They recommend 87 min. I'll often, since I have to put my card through twice, put half and half or thereabouts. Slightly more dough but better performance and some say better mileage. Share this post Link to post Share on other sites
wolfe10 Report post Posted March 20, 2012 Where were you-- or more specifically, what was the altitude? Octane requirements decrease with altitude as does octane at the pumps. Brett Share this post Link to post Share on other sites
ramblinboy Report post Posted March 20, 2012 Scipio, UT for a fill. It does seem that elevation does seem to play a part in octane requirements but beware the advertised price is for a lower octane fuel. Share this post Link to post Share on other sites
wolfe10 Report post Posted March 20, 2012 Scipio, UT shows to be at 5,270', so lower octane is not unexpected. Altitude/thinner air lowers effective compression ratio and therefore octane requirements. Only problem occurs if you fill up with low octane fuel and then drive to lower elevation, particularly if there are steep or long up-grades to pull at the lower elevation. A quick "Google" of "octane altitude" brought up this: United States: in the US octane rating is displayed in AKI. In the Rocky Mountain (high elevation) states, 85 AKI (90 RON) is the minimum octane, and 91 AKI (95 RON) is the maximum octane available in fuel[citation needed]. The reason for this is that in higher-elevation areas, a typical naturally aspirated engine draws in less air mass per cycle because of the reduced density of the atmosphere. This directly translates to less fuel and reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill a carbureted car that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains, but at sea level the fuel may cause damage to the engine. Share this post Link to post Share on other sites
hermanmullins Report post Posted March 20, 2012 Are you sure it didn't say E85. If so that means 85% Ethanol. E85 can only be used in Flex-Fuel engines. Share this post Link to post Share on other sites
ramblinboy Report post Posted March 20, 2012 Yup she were 85 Octane all right. Seems Utah uses a lot of it - as Brett mentioned elevation and combustion issues. Heres some food for thought: "Modern cars are designed to run on 85-87 octane fuel. But...there's a catch here, which may or may not affect you. Most cars have a knock sensor on the engine block. When ping or knock occurs, it tells the computer, which retards the engine timing just enough to stop the knock. On level ground, there is no difference as far as fuel economy or performance is concerned. There are situations, however, when lower octane fuel is not as good an idea. One such situation is when your driving involves lots of long uphill climbs. In those cases, where the engine is working hard, the automatic retarding of the ignition will rob your car of some power, since retarding the ignition generally reduces the power output of the engine. A similar situation occurs when you are heavily loaded or pulling a heavy trailer. Pinging or knocking may occur here as well, since the engine is working harder. Again, the retardation of the ignition will reduce power and mileage. Engines running under retarded ignition conditions also run hotter, which may be a factor as well, depending on conditions. So...for most driving, the lower octane fuel is just fine. You'll never notice the difference. But, under heavy loading conditions, like the ones described above, selecting a higher octane gasoline will result in better mileage, more power, and less chance of overheating." Share this post Link to post Share on other sites
five Report post Posted March 30, 2012 Running at altitude requires, and actually vehicles runs better, with a lower octane. That's why reciprocating aircraft engines have a mixture control. As you climb, the mixture is leaned by a control lever, so it is not as 'rich'...the octane is lower. Share this post Link to post Share on other sites
dwightginnyputzke Report post Posted March 31, 2012 no comment Share this post Link to post Share on other sites
neoflyer Report post Posted July 29, 2015 Chevy Vortec 5.3. I live near sea level. Am in Salt Lake City this week and filled up with the lowest price gas without noticing the octane. It was 85. Well, I hadn't planned using the fuel as I am towing it behind my motorhome and will probably have most of the fuel when I get to sea level again. Plan on doing most of my driving along the Oregon coast so it will probably be OK. Just wish I had noticed the octane. Share this post Link to post Share on other sites
manholt Report post Posted July 29, 2015 neoflyer, Welcome to the Forum. When in doubt, re read Brett. Luck! Share this post Link to post Share on other sites
desertdeals69 Report post Posted July 30, 2015 Chevy Vortec 5.3. I live near sea level. Am in Salt Lake City this week and filled up with the lowest price gas without noticing the octane. It was 85. Well, I hadn't planned using the fuel as I am towing it behind my motorhome and will probably have most of the fuel when I get to sea level again. Plan on doing most of my driving along the Oregon coast so it will probably be OK. Just wish I had noticed the octane. It should have a knock sensor that retards timing so all you would notice is a slight reduction in power. Share this post Link to post Share on other sites
